Thermoplastic resins having a polybutylene terephthalate (PBT) component, such as PBT itself and copolyetherester elastomers having PBT blocks, are used increasingly as engineering polymers in diverse end uses, including the automotive industry. Such resins may in particular be used in automobile interiors. Copolyetherester elastomers, for example, are widely used in air-bag deployment doors.
Many thermoplastic resins suffer the disadvantage that moulded articles made from the resins exhibit a phenomenon known as outgassing. Outgassing is the emission of organic molecules of relatively low molecular weight into the surrounding environment. Outgassing is considered disadvantageous because many of the components that are emitted have unpleasant odours, or may be irritants. PBT-containing resins are particularly prone to emit tetrahydrofuran (THF), particularly within the first weeks after moulding. Outgassing is usually worsened if the resin is used under conditions of elevated temperature (i.e. above 100° C.). Automobile manufacturers are adopting increasingly strict requirements as regards to outgassing in automobile interiors.
European patent no. EP 0 683 201 (Polyplastics Co. Ltd.) describes a method for reducing gas (particularly THF) in moulded articles made of PBT. The method involves adding a compound of Formula I, II or III during polymerisation of the monomers to make PBT:R1—SO3M  (I)
R1—O—R2—SO3M  (III)
A need remains for methods for reducing outgassing in PBT-containing thermoplastic resins.